Improvement in watch-case backs



v.and State of New Jersey, have invented a my improved watch-case caps or backs, showthe manufacture of watch-case caps and backs proiecting central springpiston or bolt, which UNITED STATES PATENT OFFICE.

HENRY BIRNN, 0F JERSEY CITY HEIGHTS, NEW JERSEY.

irlwifzoviaiviENT` IN WATCH-CASE eAcKs.

Specification forming part o f Letters Patent lNo. 154,636, dated September 1, 1874; l application' filed K February @Asn C.

To all whom' it may concern:

Be it known that I, HENRY BIRNN, of Jerv` sey City Heights, in 'the county of Hudson new and useful Improvement in the Manufacture of latch-Case Caps and Backs, of which the following is' a specification: f

In the accornpanyin,gfv dra'ving,y Figure l, 2, and 3 represent` vertical central sections of ingthern in different stages in passing,` through the' dies; and Fig. 4 shows a vertical central section of the die and punch for producing the r'solid tapering` snap of the caps and backs.Y v

Similar letters of reference indicate corresponding parts. y

The object of this invention is to so improve that the saine may be produced with greater rapidity and with increased strength at Lthe outer circumference, without soldering,` the snaps to the same.

In the drawing, A .represents the watchcase caps or backs, of the usual shape andsi'ze in common use. A blank of the size and thickness required is punched out of any sheetmetal commonly used for watch-cases, and first struck up with an outer iange, a, as shown in Fig. l. The blank is then transferred into the die B,(shown in Fig. 4,) whose. punch B .has a tapering rim, b, with a slightlytogether form an anguiar recess with inclined side. The stroke oi" the punch on the liange est strain.

of the bla'nk carries the saine to the inside, under thesam'e'inclination as that of its rim,

and produces thereby a solid snap of triangular shape, whichincreases in thickness toward the outer circumference of the cap or back, and strengthens the same at the point of greatpi voted lever, lifting the movable center bolt, and transferred tothe common concave die for producing theconvex shape of theback' or cap,which throws also the snap-ring stillv more to the inside into its regular position,

parallel tothe body of the cap or back.

The greater strength of the caps and backs produced in this manner allows the easier -application of the hinge and other devices con- .lnecting it to the watch-case center, While dis -pensing entirely with the soldering` on of the snap and thedefects connected therewith, and producing a vast saving of timel and labor in their manufacture.

Having thus described myinvention, I

claim as new, and desire to secure by Letters Patent- The one-piece cap' or back, having solid anguiar snap, increasing in thickness toward the vouter circumference, and thus strengthening the saine at the point of'greatest strain.`

HENRY BIRNN.

Witnesses GEORG P. KAISER, ROBERT F. LAIRD.

The blank lis detached from thev Idie B by a'slight stroke of the hammer on the 

